This invention relates generally to a depth of drive control for use with a fastener driving tool, and in particular, to a novel device which can be easily adjusted by the operator to control the depth of penetration of the fastener into a workpiece.
Powered fastener driving tools for driving staples, nails, and the like are very widely used today whenever it is necessary to fasten pieces of wood together. Tools of this type are generally equipped with a safety on the nosepiece which prevents the tool from actuating unless the nosepiece is in contact with a workpiece.
One problem which arises when using tools of the type previously described results from the fact that each fastener is driven from the tool with the same energy each time that the tool is actuated. This will cause fasteners to be driven to an inconsistent depth if there is a significant variation in the density of the material into which the fasteners are to be driven; or if a worker is using a combination of wood types (soft and hard) for a particular application. In addition, sometimes it is desirable to countersink the head of a nail beneath the surface of the workpiece. It is possible to compensate for this by adjusting the air pressure supplying the tool; however, this method is time consuming, and is difficult to accurately determine the proper pressure setting to reach the desired depth of drive for each fastener.
The problem of controlling the depth of drive for fastener driving tools has been addressed in the prior art. U.S. Pat. No. 3,519,186 which issued Jul. 7, 1970, to Dieter Volkmann, teaches a pneumatic fastener driving tool in which a notched plate is moveable longitudinally with respect to the from plate and the drive track of the tool. The from plate and the notched plate are each provided with knurlings or corrugations such that it is possible to adjust the notched plate in any desired position relative to the front plate. However, as the two plates are maintained in position by a series of screws, it is necessary to use tools to adjust the position of the plates when it is desired to vary the depth of drive, which can be time consuming if it is often necessary to vary the depth during a particular application.
This problem was addressed again in U.S. Pat. No. 4,7677,043, which issued to Prudencio S. Canlas, Jr. on Aug. 30, 1988. This patent teaches a manual adjusting mechanism for the work contacting element of a fastener driving tool which includes a manually operable member movable by manual engagement to effect an adjustment of the adjusting mechanism and a releasably lock movable between a locking position for locking the manually operable member against manual movement and a releasing position enabling the manually operable member to be manually moved. This is accomplished in the invention by a door which, when closed, allows a leaf spring to lock the adjusting mechanism in place and when opened, shifts the leaf spring away from the adjusting mechanism to allow for manual rotation. While this device is effective to allow adjustment of depth of drive, it requires that a section of the tool be opened for access to the adjusting mechanism.
Another example of a depth of drive adjustment for a fastener driving tool is taught in U.S. Pat. No. 5,219,110, which issued Jun. 15, 1993, to Kenji Mukoyama. This mechanism for adjusting drive depth includes a cam device interposed between an upper part and a lower part of the workpiece contacting element. The cam device, which consists of an upper cam and a lower cam, is manually rotatable to vary the depth of penetration of fasteners into a workpiece.
While each of the aforementioned prior art devices allows for adjustment of the driving depth for a fastener driving tool, they all suffer from undesirable characteristics, such as the need for additional tools, the necessity to open part of the tool to gain access, or unnecessary complexity of the mechanism to accomplish the desired adjustment.